Air in pumped hot water system.


Postby gotabelt » Mon Dec 21, 2009 7:19 pm

Good evening,

I have a pumped hot water system but the water is spurting from the taps due to an ingress of air which I believe is being drawn in via the expansion pipe. I recently fitted an automatic air bleed valve underneath an upstairs tap (the highest point in the system) and followed the directions exactly but the problem remains. Would it be possible to fit a vertical check valve to the expansion pipe which would allow excess hot water to discharge into the tank but would restrict air being dtawn in when the pump is running. NOW three questions for the experts. Firstly is my diagnosis feasible and secondly would a check valve solve the problem. Finally if a valve would work where can I get one? the expansion pipe is 15mm dia.

REgards

Peter
gotabelt
Posts: 31
Joined: Sun Dec 16, 2007 5:50 pm

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Postby rosebery » Thu Dec 24, 2009 11:13 am

"I have a pumped hot water system but the water is spurting from the taps due to an ingress of air which I believe is being drawn in via the expansion pipe."

That is a distinct possibility and if so, thats all to do with the way it has been piped. How is it piped?


"I recently fitted an automatic air bleed valve underneath an upstairs tap (the highest point in the system) and followed the directions exactly but the problem remains."

Yes that won't help.


"Would it be possible to fit a vertical check valve to the expansion pipe which would allow excess hot water to discharge into the tank but would restrict air being dtawn in when the pump is running."

Yes it is possible to do it. There are three reasons why you shouldn't. First is its dangerous, the 2nd is that its dangerous and the third is that its dangerous.


"NOW three questions for the experts. Firstly is my diagnosis feasible and secondly would a check valve solve the problem. Finally if a valve would work where can I get one? the expansion pipe is 15mm dia."

You diagnosis is prolly correct. No you should not fit a check valve. We need to examine how the pump is piped and how that can be corrected to avoid drawing the air in. Can you draw an accurate word picture or alternatively take a couple of pics, host on imageshack or photobucket and post a link here.

Cheers
rosebery
Posts: 2022
Joined: Wed Sep 26, 2007 8:55 pm


Postby gotabelt » Sun Jan 03, 2010 12:43 pm

Hi,

I will try to describe the system. It is fairly bog standard.

The hot water tank is on the ground floor (actually almost sitting on the floor) with the pump sited next to it.

The feed to the pump is teed off the top of the tank with the expansion leg going up through the ceiling to discharge into the header tank.

The supply to the taps obviously runs around the ground floor to various taps and upstairs to supply the en-suite sink.

I have a drawings in PDF and MS Publisher but I don't think the admisnistrators allow them to be posted on here.


Thanks for your interest.
Peter
gotabelt
Posts: 31
Joined: Sun Dec 16, 2007 5:50 pm


Postby rosebery » Sun Jan 03, 2010 2:06 pm

"The feed to the pump is teed off the top of the tank with the expansion leg going up through the ceiling to discharge into the header tank."

This is the key to it all. Some short distance up that pipe there is a right angled tee joint where the water is drawn off for your bathroom and kitchen taps.

If you have teed your shower supply at another point off the vertical section of pipe the pump will be drawing air down the vent as well as water up from the cylinder. If you have teed off your shower supply from the taps supply you could well be doing the same thing.

Is that how it has been done?

Cheers
rosebery
Posts: 2022
Joined: Wed Sep 26, 2007 8:55 pm


Postby rosebery » Sun Jan 03, 2010 2:11 pm

You are correct about your documents but they prolly wouldn't help anyway being schematic. Can you not take a pic of the cylinder / pump area? It may not matter - your reply to my earlier post may give us the answer.

Cheers
rosebery
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Joined: Wed Sep 26, 2007 8:55 pm


Postby gotabelt » Fri Jan 08, 2010 10:49 am

Hi Rosebury,

My description of where the hot water is taken from the tank is not quite correct. Remember this dwelling used to be a bungalow built in the late 60's. The hot water is taken from the pipe which comes from the top of the tank but this pipe runs down behind the tank to the floor and then (before I installed the pump) went into the floor and laid in channels in the floor held in place with a soft screed. I broke into the pipe approx 18" from the floor to feed the pump. You mention the shower, this comes off the output side of the pump. Taking photo's is difficult due to space restrictions but I have put some photos on Photobucket but I don't know how you access them, do you?

Why is it dangerous to put check valves into expansion pipes. Is it due to the possibility of them sticking?

<a href="http://s960.photobucket.com/albums/ae86/bowler78/?action=view&current=Breakinpoint.jpg" target="_blank"><img src="http://i960.photobucket.com/albums/ae86/bowler78/Breakinpoint.jpg" border="0" alt="Take off point to pump"></a>

<a href="http://s960.photobucket.com/albums/ae86/bowler78/?action=view&current=Pumppipework3.jpg" target="_blank"><img src="http://i960.photobucket.com/albums/ae86/bowler78/Pumppipework3.jpg" border="0" alt="Pump Pipework 1"></a>

I may have been able to copy images onto here.

Regards
Peter
gotabelt
Posts: 31
Joined: Sun Dec 16, 2007 5:50 pm


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